(a) Explain the phenomena of multiple allelism and co-dominanace

Subject

Biology

Class

CBSE Class 12

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 Multiple Choice QuestionsShort Answer Type

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26.

(a) Explain the phenomena of multiple allelism and co-dominanace taking ABO blood group as an example.

(b) What is the phenotype of the following:

(i) IAi

(ii) i i


(a) The inheritance of ABO blood groups in humans exhibits co-dominance and multiple allelism.

Multiple allelism-: The ABO blood groups are controlled by the gene I. The I gene has three alleles, namely IA, IB and i. Since more than two alleles control a single trait thus it shows multiple allelism.

Co-dominance-: The allele IA and IB are both dominant over the allele i but they express themselves completely even in the presence of the other that is when both are present the blood group is AB . This represents co-dominance.

(b) ( i) Phenotype of IAi will be A blood group since the allele IA is dominant over the allele i

(ii) Phenotype of ii will be O blood group since the allele is recessive and expresses itself in the homozygous condition.
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 Multiple Choice QuestionsLong Answer Type

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